In induced draft furnaces, a motor driven inducer blower may be provided to enhance the mixing of combustion air with the fuel in order to better facilitate the combustion process. While the inducer blower may be located upstream and be of the blow-through type, it is more common to place it downstream of the combustion process so as to draw the supply air into the burner and cause the combustion gases to flow through the heat exchangers and the vent pipe to be discharged outside.
Induced draft furnaces may employ a furnace inducer choke to help control the amount of combustion air entering the induced draft furnace. As a given size inducer blower may be used for a variety of different sized induced draft furnaces (e.g., to simplify the manufacturing process) the inducer chokes tend to be removable and interchangeable. Unfortunately, the location and positioning of the inducer blower, and more specifically, inducer choke when installed in the inducer blower, make it difficult to determine what size choke is being used for a given installation.